The present invention is directed toward a need, as we conceive it, for a retroreflective treatment for fabrics that is so inconspicuous in daylight and of so little effect on hand, feel, and breathability, that garments made from the fabric will be widely worn by pedestrians; and that yet is so brightly retroreflective that the pedestrians will be readily visible at night for several hundred feet and more under illumination from oncoming motorists.
The need to increase the visibility of pedestrians walking along streets or highways at nighttime has long been recognized. A three-year study of 12 United States cities having populations of more than 500,000 found that 50 percent of the total nighttime traffic fatalities were pedestrian deaths.sup.1 (footnote references are at the end of the specification). And the accident rate per million vehicle-miles for all fatal and serious traffic accidents is 21/2 to 3 times higher at night than it is during the day.sup.2. The low visibility of pedestrians during hours of darkness is a major factor in these statistics.
Reflectorized clothing would greatly increase the visibility of pedestrians at nighttime. Tests have demonstrated that motorists detect pedestrians clothed in reflectorized garments much earlier than they detect pedestrians clothed in nonreflectorized clothing. In one test,.sup.3 pedestrians were simulated by placing boxes 12 inches by 12 inches by 48 inches (30 by 30 by 120 centimeters) covered with different test fabrics along a course traveled by test observers in cars. The fabrics tested were black, grey, white, and grey with a strip of silver reflectorized tape 1 inch by 11 inches attached horizontally 15 inches from the ground. The results of the tests in terms of the percentages of pedestrians who were safely visible to test observers at distances greater than "critical visibility distances" (reaction distance plus braking distance) are summarized in the following table:
______________________________________ Simulated Miles per Hour Pedestrians 20 40 60 80 ______________________________________ Black 86.4 45.4 0 0 Grey 100 47.2 5.5 0 White 100 100 97.2 52.7 Reflectorized 100 100 100 100 ______________________________________
The problem is that very few persons wear reflectorized garments. Such garments were available at least by the late 1940's, and many efforts have been made over the years to promote their use. Only limited success has resulted from these efforts, undoubtedly because existing commercial reflective treatments for garments are conspicuous in daytime and do not permit a desired variety in fashion.
Retroreflective tapes have provided the most accepted way to reflectorize garments. These tapes typically comprise a monolayer containing many thousands of glass microspheres per square centimeter supported over specular reflective means in a flexible binder material (see Palmquist et al, U.S. Pat. No. 2,567,233, later patents teaching improved varieties include Bingham et al, U.S. Pat. No. 3,551,025, which teaches a wet-or-dry reflecting material having a flexible transparent flat-surfaced top layer over the layer of microspheres; Bingham, U.S. Pat. No. 3,700,305, which teaches the use of visibly transparent but reflective dielectric layers as the specular reflective means, and thus makes possible more variety in the underlying color of retroreflective materials; and Bingham, U.S. Pat. No. 3,758,192 which teaches retroreflective materials that use nacreous pigments underneath the microspheres to provide retroreflectivity while permitting variety in the color of the material). These tapes ordinarily have little resemblance to fabric to which they are applied, and their use on fabrics has generally been limited to situations where they serve as trim that is part of an ornamental design for the garment. By far the majority of outerwear garments do not use such tapes.
Limited or strip reflectorization can also be provided, as taught in Longlet et al, U.S. Pat. No. 3,535,019, with liquid coating compositions that comprise hemispherically-aluminum-covered glass microspheres dispersed in a water-emulsion of a flexible thermoplastic resin. Such liquid coating compositions have not been commercially successful probably because, as the patent states, "some relative stiffening of the fabric occurs in the area of the applied marking" (column 1, lines 61 and 62), and because the markings contemplated cause daytime conspicuity.
In a different approach, it has been suggested that pellets of a synthetic resin- or elastomer-based paste dissolved in a solvent be pressed onto a foil such as may be used for raincoats, after which glass microspheres are sprayed onto the pellets; see Swiss Pat. No. 514,731. Like other approaches, this suggestion contemplates visibly apparent treatments, but suggests use of forms that will contribute to decoration of the foil.
In another approach tried without success, retroreflective sheeting carrying a heat-activatable adhesive on its back surface was chopped into approximately 1/16-inch or 1/8-inch segments; the segments sprinkled onto a first piece of fabric; a second piece of the fabric laid over the sprinkled area; and the assembly heated and pressed, as with an iron. The retroreflective segments thus became adhered to one of the pieces of fabric, depending by chance on which fabric their adhesive side faced. Success was lacking, among other reasons, because the treatment was rather unattractive, with a scattering of irregularly shaped conspicuous segments; and the method was not adapted to rapid processes; e.g., the segments tended to clump together and did not cascade freely, apparently because the binder material of the segments was soft and flexible.
Others have suggested reflectorizing the whole fabric of a garment, but insofar as known, none of these has proved commercially or otherwise feasible. Carey et al, U.S. Pat. No. 2,937,668 teaches glass-microsphere-enveloped yarns for inclusion in small proportion with conventional yarns to form a composite fabric that could be made into garments. For a variety of reasons, such a technique has never been commercially successful. McGaugh, U.S. Pat. No. 2,581,549 suggests adhering conventional retroreflective sheeting over the back portion of a glove to provide brilliantly retroreflective signaling gloves, where daytime conspicuity is not an obstacle. Tung, U.S. Pat. No. 3,790,431 describes a reflectorized open-mesh fabric that is useful for many purposes, but as wearing apparel is generally used only as brilliantly retroreflective vests or jackets for police or highway construction or maintenance workers.
Certain decorative fabrics from the prior art have exhibited a limited reflectivity but not the retroreflectivity (a return of light along essentially the same path that the light traveled to the reflector, which, for example, provides a brilliant reflection to the driver of an automobile whose headlamps illuminate the reflector) that is needed to provide pedestrian safety. For example, Kaphan, U.S. Pat. No. 2,582,132 teaches ornamental "studded" fabrics that have enlarged round glossy plastic elements adhered over the surface of the fabric for decorative effects. Glass beads have also been adhered to fabrics for decorative effects, as indicated by Kukoff, U.S. Pat. No. 3,377,184, which suggests the use of plastic particles instead; but these beads have not been used in combination with underlying reflective means needed to turn the glass beads into a brilliantly retroreflective element. None of these decorative fabrics would appear to have any useful retroreflective effects.
In summary, no one has previously suceeded in providing a retroreflective treatment for wearing apparel that would both provide desired levels of safety and be fashionably acceptable over a wide range of outerwear garments. Until there is such a treatment, there can apparently only be limited improvements in pedestrian visibility at nighttime.